dtgsna(3) on Linux
The text 74bc96f82197, as Debian 4.0 (Etch), Debian 3.1 (Sarge) shipped it.
estimate reciprocal condition numbers for specified eigenvalues and/or eigenvectors of a matrix pair (A, B) in generalized real Schur canonical form (or of any matrix pair (Q*A*Z', Q*B*Z') with orthogonal matrices Q and Z, where Z' denotes the transpose of Z